clean up docstring and test descriptions

Author: yucongalicechen

src/diffpy/utils/scattering_objects/diffraction_objects.py

@@ -366,9 +366,7 @@ def tth_to_q(self):
 
     def q_to_d(self):
         r"""
-        Helper function to convert q to d using :math:`d = \frac{2 \pi}{q}`
-
-        adds a small value (epsilon = 1e-10) to `q` where `q` is close to zero to avoid division by zero
+        Helper function to convert q to d using :math:`d = \frac{2 \pi}{q}`, set dmax to DMAX=100
 
         Parameters
         ----------
@@ -387,9 +385,7 @@ def q_to_d(self):
 
     def d_to_q(self):
         r"""
-        Helper function to convert d to q using :math:`q = \frac{2 \pi}{d}`
-
-        adds a small value (epsilon = 1e-10) to `d` where `d` is close to zero to avoid division by zero
+        Helper function to convert d to q using :math:`q = \frac{2 \pi}{d}`, set qmax to QMAX=40
 
         Parameters
         ----------
@@ -410,8 +406,7 @@ def tth_to_d(self):
         r"""
         Helper function to convert two-theta to d
 
-        uses the formula .. math:: d = \frac{\lambda}{2 \sin\left(\frac{2\theta}{2}\right)},
-        and adds a small value (epsilon = 1e-10) to sin where sin is close to zero to avoid division by zero
+        uses the formula .. math:: d = \frac{\lambda}{2 \sin\left(\frac{2\theta}{2}\right)}, set dmax to DMAX=100
 
         Parameters
         ----------
@@ -438,8 +433,7 @@ def d_to_tth(self):
         r"""
         Helper function to convert d to two-theta
 
-        uses the formula .. math:: 2\theta = 2 \arcsin\left(\frac{\lambda}{2d}\right),
-        and adds a small value (epsilon = 1e-10) to `d` where `d` is close to zero to avoid division by zero
+        uses the formula .. math:: 2\theta = 2 \arcsin\left(\frac{\lambda}{2d}\right), set tth to 180 when d=0
 
         Parameters
         ----------
@@ -465,17 +459,17 @@ def set_all_arrays(self):
             self.on_tth[0] = self.q_to_tth()
             self.on_tth[1] = master_array[1]
             self.on_d[0] = self.q_to_d()
-            self.on_d[1] = master_array[1]
+            self.on_d[1] = master_array[1][::-1]
         if xtype == "tth":
             self.on_q[0] = self.tth_to_q()
             self.on_q[1] = master_array[1]
             self.on_d[0] = self.tth_to_d()
-            self.on_d[1] = master_array[1]
+            self.on_d[1] = master_array[1][::-1]
         if xtype == "d":
             self.on_tth[0] = self.d_to_tth()
-            self.on_tth[1] = master_array[1]
+            self.on_tth[1] = master_array[1][::-1]
             self.on_q[0] = self.d_to_q()
-            self.on_q[1] = master_array[1]
+            self.on_q[1] = master_array[1][::-1]
         self.tthmin = self.on_tth[0][0]
         self.tthmax = self.on_tth[0][-1]
         self.qmin = self.on_q[0][0]

tests/test_diffraction_objects.py

@@ -250,19 +250,19 @@ def test_tth_to_q():
 
 
 def test_q_to_d():
-    actual = Diffraction_object(wavelength=0.71)
+    actual = Diffraction_object()
     setattr(actual, "on_q", [[0, np.pi, 2 * np.pi, 3 * np.pi, 4 * np.pi, 5 * np.pi], [1, 2, 3, 4, 5, 6]])
     actual_d = actual.q_to_d()
-    # expected d values are DMAX=100, 2/1, 2/2, 2/3, 2/4, 2/5, and in reverse order
+    # expected d values are DMAX=100, 2/1, 2/2, 2/3, 2/4, 2/5, in reverse order
     expected_d = [0.4, 0.5, 0.66667, 1, 2, 100]
     assert np.allclose(actual_d, expected_d)
 
 
 def test_d_to_q():
-    actual = Diffraction_object(wavelength=1)
+    actual = Diffraction_object()
     setattr(actual, "on_d", [[0, np.pi, 2 * np.pi, 3 * np.pi, 4 * np.pi, 5 * np.pi], [1, 2, 3, 4, 5, 6]])
     actual_q = actual.d_to_q()
-    # expected q values are QMAX=40, 2/1, 2/2, 2/3, 2/4, 2/5, and in reverse order
+    # expected q values are QMAX=40, 2/1, 2/2, 2/3, 2/4, 2/5, in reverse order
     expected_q = [0.4, 0.5, 0.66667, 1, 2, 40]
     assert np.allclose(actual_q, expected_q)
 
@@ -281,7 +281,7 @@ def test_d_to_tth():
     setattr(actual, "on_d", [[0, 2, 4, 6, 8, 100], [1, 2, 3, 4, 5, 6]])
     actual_tth = actual.d_to_tth()
     # expected tth values are 2*arcsin(1/d), in reverse order
-    # when d is really small we have tth to be 180
+    # when d is 0, we set tth to 180
     expected_tth = [1.14593, 14.36151, 19.18814, 28.95502, 60, 180]
     assert np.allclose(actual_tth, expected_tth)